Add gdb helper functions for creating a handle and using ToCString with RawObjects.

runtime/vm/gdb_helpers.cc

Index: runtime/vm/gdb_helpers.cc
diff --git a/runtime/vm/gdb_helpers.cc b/runtime/vm/gdb_helpers.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b50d912e0edf5010d2db0204e46cfde31ca88760
--- /dev/null
+++ b/runtime/vm/gdb_helpers.cc
@@ -0,0 +1,81 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "lib/stacktrace.h"
+#include "vm/object.h"
+#include "vm/stack_frame.h"
+
+namespace dart {
+
+#if !defined(PRODUCT)
+
+DART_EXPORT
+void _printRawObject(RawObject* object) {
+  OS::PrintErr("%s\n", Object::Handle(object).ToCString());
+}
+
+
+DART_EXPORT
+Object* _handle(RawObject* object) {
+  return &Object::Handle(object);
+}
+
+
+// An utility method for convenient printing of dart stack traces when
+// inside 'gdb'. Note: This function will only work when there is a
+// valid exit frame information. It will not work when a breakpoint is
+// set in dart code and control is got inside 'gdb' without going through
+// the runtime or native transition stub.
+DART_EXPORT
+void _printDartStackTrace() {
+  const StackTrace& stacktrace = GetCurrentStackTrace(0);
+  OS::PrintErr("=== Current Trace:\n%s===\n", stacktrace.ToCString());
+}
+
+
+// Like _printDartStackTrace, but works in a NoSafepointScope. Use it if you're
+// in the middle of a GC or interested in stub frames.
+DART_EXPORT
+void _printStackTrace() {
+  StackFrameIterator frames(StackFrameIterator::kDontValidateFrames,
+                            Thread::Current(),
+                            StackFrameIterator::kNoCrossThreadIteration);
+  StackFrame* frame = frames.NextFrame();
+  while (frame != NULL) {
+    OS::PrintErr("%s\n", frame->ToCString());
+    frame = frames.NextFrame();
+  }
+}
+
+
+class PrintObjectPointersVisitor : public ObjectPointerVisitor {
+ public:
+  PrintObjectPointersVisitor() : ObjectPointerVisitor(Isolate::Current()) {}
+
+  void VisitPointers(RawObject** first, RawObject** last) {
+    for (RawObject** p = first; p <= last; p++) {
+      Object& obj = Object::Handle(*p);
+      OS::PrintErr("%p: %s\n", p, obj.ToCString());
+    }
+  }
+};
+
+
+DART_EXPORT
+void _printStackTraceWithLocals() {
+  PrintObjectPointersVisitor visitor;
+  StackFrameIterator frames(StackFrameIterator::kDontValidateFrames,
+                            Thread::Current(),
+                            StackFrameIterator::kNoCrossThreadIteration);
+  StackFrame* frame = frames.NextFrame();
+  while (frame != NULL) {
+    OS::PrintErr("%s\n", frame->ToCString());
+    frame->VisitObjectPointers(&visitor);
+    frame = frames.NextFrame();
+  }
+}
+
+#endif  // !PRODUCT
+
+}  // namespace dart